Alignment apparatus

Abstract

An apparatus for moving a stage, supported by a base, to a target position. The apparatus includes a motor for driving the stage in X and Y directions, a laser interferometer for measuring a current position of the stage in the X and Y directions and a controller for generating a control signal for controlling the motor to move the stage to the target position in the X and Y directions on the basis of the target position and for dynamically setting a transfer function associated with generation of the control signal in correspondence with the current measured position. The controller sets the transfer function so that a gain decreases as the stage moves toward a peripheral portion of the base.

What is claimed is: 
     
       1. An apparatus for moving a stage, supported by a base, to a target position, said apparatus comprising: a motor for driving the stage in X and Y directions;   a laser interferometer for measuring a current position of the stage in the X and Y directions; and   a controller for generating a control signal for controlling said motor to move the stage to the target position in the X and Y directions on the basis of the target position, and for dynamically setting a transfer function associated with generation of the control signal in correspondence with the current measured position,   wherein said controller sets the transfer function so that a gain decreases as the stage moves toward a peripheral portion of the base.   
     
     
       2. The apparatus according to claim 1, wherein said controller generates the control signal by feeding back the current measured position. 
     
     
       3. The apparatus according to claim 2, wherein said controller generates the control signal by amplifying a difference between the target position and the current measured position in accordance with the transfer function. 
     
     
       4. The apparatus according to claim 3, wherein said controller sets the transfer function on the basis of a predetermined function which defines the transfer function corresponding to the current measured position. 
     
     
       5. The apparatus according to claim 4, wherein the transfer function includes proportional, integral, and derivative elements, and said controller sets the proportional, integral, and derivative elements of the transfer function on the basis of the predetermined function. 
     
     
       6. The apparatus according to claim 3, wherein said controller sets the transfer function on the basis of a predetermined table which defines the transfer function corresponding to a region including the current measured position. 
     
     
       7. The apparatus according to claim 6, wherein the transfer function includes proportional, integral, and derivative elements, and said controller sets the proportional, integral, and derivative elements of the transfer function on the basis of the predetermined table.